Bearings with journal supporting elements of glass



Jan. 15, 1963 H. B. wHlTr-:HURST BEARINGS WITH JOURNAL SUPPORTING ELEMENTS OF GLASS Filed March 25, 1959 /fo \////o//a// INV E NTOR. HMW WH/rn/usr BY WA v Arrow/frs Uflid States Patent Otis@ l 3,073,658 Patented Je@ .15 .195?" .3,073,653 BEARINGS WITHJOURNAL SUPGRTING ELEMENTS F GLAS?, i e I Harry B. Whitehurst, Phoenix, Ariz., assigner to Owens- Corning Fiberglas Corporation, a corporation of Delaware Filed Mar. 25, 1959, Ser, No.r8l,947 6 Claims. (Cl. 30S- 237) This invention relates generally to plain bearings which are commonly of split sleeve design but made by of solid sleeve construction or formed Within heavy mountings usually of cast iron.

More specilically, this invention deals with plain bearings in which the main component is a relatively soft metal such as lead or tin and there is 'a minor but very important component of dispersed particles of hard substances. Babbitt or white met-al stock are the' bes't known examples of such bearing compositions, and this invention, especially but not exclusively involves the addition or substitution of glass fibers for the :hard metallic substances of the Babbitt alloys. I

The plastic quality of lead, tin, cadmium or other soft metals is most `desirable in a bearing as it permits yielding to irregularities in the contour of the supported shaft and absorbs gritty panticles ne'achinrg the bearing sunace ywhich may score the shaft. The soft metal content of the bearing composition thus protects and conforms With the shaft, and the journal load is distributed evenly over the bearing surface.

The soft quality of these metals, however, is evidenced undesirably in the main body of bea-rings in cold flowing under high pressures Kat room temperatures land in a'ccelerated flowing at higher temperatures. This deformation is facilitated by recrystallization growth inherent with these elements.

The inclination to how of the soft matrix inctals is lessened and the low tensile and fatigue strengths thereof are fortified through the incorporation of the hardening agents, and by backings of steel or bronze. In fact, the yadditive materials really make it possible to use the low melting metals as basic bearing stock.

In this regard, cadmium, whichl is not utilized extensively because of several adverse factors including those of cost and limited supply, is strengthened by very small increments of nickel, or copper Vand silver. For bearing use, a tin base is made more sturdy by being alloyed with antimony and copper, the quantities of these additives generally amounting to about eight percent of antimony and four to -six percent of copper. The reinforcing elements usually combined with lead includes nine percent or more of antimony, vaiying amounts of tin with an' average or" ten percent, less than one percent or copper, and about one percent of arsenic. Y

The structure of these alloys is heterogeneous, normally containing dispersed hard crystals of the additive inetals in a softer matrix of the ba'sic metal. The crystals are cubic when tfornied of tin and antimony, and needle shaped when compounded of copper and tin. The needleshaped particles of copper and tin entrain the tin-antimony cubes, discouraging iloating segregation of the latter arising from their low specific gravity during the molten istate of the alloy.

The spaced grains or crystals of the hard metals in the surface of the bearing have the' very essential purpose of sustaining the lo'ad. At points of extra pressure the more plastic matrix yields `beneath the crystals :and conforms the bearing area to the shaft. The give of the matrix also provides channels for lubricants. j

Lf there are only a few hard grains in the4 metal composition it will be too soft `and -will stand only low bear- 2 ing pressures. Should there be too large v'a quality lof the hard grains the points of the crystals will engage one another and form a solid network with objectionable ibrittleness. e

The crystalline `co'riiponentfs make the bearings more resistant to mechanical injuries and 'abrasione e The tensile properties and fatigues strengths are improved to a moderate degree while the tendency of the soft base metals to cold flow is ameliorated. The more favorable properties of the base metals are accordingly desirably retained to an extent that allows thebearing 'to' 'adjust itself to the pressure of the rotating shaft, permitting rotation without excessive friction, and melting when extreme heating occurs without damage to the shaft.

With the contradictory combination or hardness fand softness in the same alloys, the babbitt bearings have given generally very reliable service and have beenpreiferably utilized in a lar'gep'roportioii of industrial machinery.

They possess fa load carrying capacity of up to ()l bearings are restricted to speeds considerably below those permissible with the babbitt bearings. e i

Accordingly, in spite of their overall excellent performance, bearings of soft metal bases have been limited in the loads 'they will sust-ain and in the temperatures at which they will operate. These deficiencies, or rather re'- strictions in capacity, are derived principal-IY,H from the 'fac-t that the' strength (if the alloys is rapidly reduced, and the ltendency of the alloysv to -creep is accelerated proportionately with a rise in temperature. l H Y Y .Y Y u It is estimated that the tensile strength sf Babbitt bearings which may be around a very vsatisfactory sixteen thousand pounds per square 'inch at room ter'nperi'aturew is cut in h'alf by a rise -to 200 Fahrenheit and thatuthecrefe'pf which will retain their desirable bearing properties `a`t` temperatnres reached under heavy stressesv and hence' be ableto continue to function properly while carrying heavier loads'.

This object as well as others ancillary thereto is attained' by the incorporationl of brous glass in place o'f or in' ad-r ditionV to 'the metallic agents :heretofore utilized. The remarkable effectiveness of a fibrous glass component even i' in very ,low quantities' such as three percent by volume i's evidently `derived from a combination of propcrtie'sincluding primarily its uniform fibrous form', and secondarily its hardness, flexibility, high tensile strength; and newly discovered bearing quality,Y which are all apparently retained at temperatures' up to 650 Fahrenheit.

As a substitutefsr the hard' metal crystals'th glass' assis Vfinist act as' hard lands iii the lead receiving siirfae of the bearings. The discevery herein involved that glass, a synonym for brittleness, serves Well as a bearingv con ety material is most unexpected. In this'conn'ection it may be considered that the load carrying portion of the bearing is of glass composition held in contact with the journal by a backing of the more plastic metal.

Straight sections, bends and no doubt some ends of the glass fibers situated in the load receiving surface of the bearing evidently provide smooth, agate-like, supporting lands comparable but evidently superior in function to those presented by the cuboid and needle crystals of antimony, tin and copper. Also by running variously through the main body of soft metal the inclination of the metal to flow is more thoroughly blocked by the fibers than they would be by the metallic grains. The tensile strength of the fibers further helps .to maintain the shape of the matrixV under heavy load stresses.

It is not a prime purpose of this invention to increase the original strength of the bearing material beyond that possessed by the conventional babbitt types as the strength of the latter is considered satisfactory, but rather to establish a stable strength that endures under higher operating temperatures and one which still does not lessen the plastic yielding properties which have been mainly responsible for the success of these bearings.

Tests indicate that a content of four percent by volume of fibrous glass spread through pure lead will provide a bearing equivalent in strength and superior in thermal resistance to one of a standard lead Babbitt composition. There will be an'objectionable loss of plasticity if too great a quantity of the fibrous glass is added or if it is used in too heavy a combination with the regular additive metallic crystals. A material is then developed having stiffness which brings the bearing product more in the class with those of bronze, and of high copper with lead which require hardened shafts, closer tolerances and better controlled lubrication.

Where the original strength of the Babbitt alloys is diminished at higher temperatures, in some manner not clearly understood the low content of fibrous glass main-- tans a high percentage Yof the bearing strength even though the metal base may approach -a semi-fluid state.

The invention will be further explained in connection with drawings in which a method of fabrication is depicted.

FIGURE 1 of the drawings is a vertical section of a heated tank containing molten metal which is being introduced into a submerged bearing mold;

FIGURE 2 is an isometric view of the graphite core utilized in the molding operation; and

vFIGURE 3 shows in perspective a split sleeve 4bearing embodying the invention as produced by the apparatus of FIGURE `l.

Referring to the drawings in more detail, there is shown in the assembly of FIGURE 1 and separately in FIGURE 2 a graphite core 10 around which is placed Vthe fibrous glass component of the bearing to be fabricated. Radial grooves 11 at the upper and lower ends of the core provide venting paths for the air to be displaced by the molten base metal and access passages for the metal.

The fibrous glass is preferably in the form of an unbound mat of randomly oriented, single fibrous in average lengths of an inch or more and with diameters between fifteen andeighty hundred thousandths of an inch. A mat of cut strands or a woven or unwoven fabric of fibrous glass may also be utilized but these are not considered as effective in function.

To insure good adhesion to the fibers by the molten lead, tin or other metal to `be cast, the fibers may carry a precoating of like metal, applied immediately following the drawing of the fibers.

The mat or thin pack of fibers which may be approxi-V mately one sixteenth of an inch thick is wrapped around the core one or more times according to the thickness of the annular bearing blank to be ca'st. The application and shaping of the mat of glass around the core is facilitated by wetting thereof.

When the bearing base metal is in a comparatively pure state and the fibrous glass is intended to provide substantially the full complement of hard points or lands to support the journal, it is recommended that the fibrous glass component comprise at leastlthree percent by volume of the bearing composition, and preferably between four and six percent thereof.

In the disclosed fabricating method, after the fibrous glass has dried, the core 10 with the glass sheath 14 thereon, is introduced into a casing 16. The main cylindrical body 17 of this casing is a finned tube of steel to constitute the conventional backing of the sleeve bearing to be constructed.

When the core 10, ringed with the fibrous glass 14 is inserted into the casing 16, the latter is not confined and is conveniently in a position inverted from that shown in FIGURE l. With the casing so positioned, the closure cap 18 forms the bottom of the casing. The core 10 is centered by being lodged within the circular flange 19 turned inwardly from the cap 18. Projecting exteriorly from the center of the cap 18 is an air exhaust nipple 21.

The opposite end of the casing 16 is then closed by a cover 23 threaded upon the cylinder 17. The cover 23 is provided with a flange 25, similar to the circular flange 19, which centrally aligns the associated end of the core 10. The fibrous glass stock is thus lodged in the annular molding space between the core 10 and the cylinder 17. Joined to the cover 23 is a bent copper tubing 27 through which molten metal enters the casing 16 to reach the annular mold cavity between the cylinder 17 and the core insert 10.

Before the mold assembly is inserted into the tank 29 in which the molten metal supply is held, the assembly is preheated at a temperature likely between 450 and 600 Fahrenheit for a period up to approximately fifteen minutes with the exact temperature and length of time depending upon the character of the base metal or alloy involved.

In case bare rather than coated glass fibers are utilized some slight alloying of the metal flux may be desirable. For instance, if a straight lead base is involved the inclusion of one percent of zinc and slightly more cadmium improves the bonding between the metal and bers.

The recommended temperature maintained in tank 29 by heating elements such as indicated at 31 varies with the identity of the metal or alloy being utilized and would ordinarily be between 600 and 920 Fahrenheit.

After the assembled mold has been immersed in the molten bath for a short interval to bring it up to a like temperature, vacuum is applied to tube 21 which extends exteriorly of the tank lid 32 through the central aperture 33 therein. The evacuation of the air from casing 16, thus effected, lessens the likelihood of air being locked between the fibers and also develops pressure assisting the flow of the molten stock into copper tube 27, radially outward along the lower grooves 11, and into the mold cavity.

The interior of the cylinder 17 has a tin coating to promote the adherence of the molten metal thereto. As soon as the base metal has filled the annular space of the mold and thoroughly encompassed the fibers therein the vaccum through nipple 21 is relieved, and the casing 16 is thrust downwardly within tank 29 to collapse and seal copper tubing 27 which has been considerably softened by the temperature of the metal flux. The lid 32 of tank 29 is then removed, and the mold casing 16 withdrawn and quenched with a water spray.

Following solidifying and cooling of the fiber impregnated casing, the ends of the casing 16 are machined to cut off the closure 18, the cap 23, and incidentally the grooved ends of the core 10. The graphite core is then removed by suitable drilling and reaming operations. The inner surface of the bearing may next be machined to the desired dimensions. If the bearing is not to be used in a full round form it is cut in half to produce two split sleeves such as that depicted at 40 in FIGURE 3.

The surface 42 of bearing 40 has minor portions of bonded. This attachement must be very thorough inr order for the strength of the backing to be effective in supporting the softer bearing material. Shells or bac-kings of bronze are also commonly employed and may just as well be used for bearings of Ithis invention.

Instead of being cast, the metal and fibrous glasscombination may be constructed in strip form and bent to shape to fit within and be bonded to a steel or bronze backing or to a cast iron mounting.

The fibrous glass may be disposed in the body only of the bearing structure leaving a thin glass-free layer on the journal receiving surface. An ingredient of metallic crystals in the bearing alloy may then serve as the direct load carrying elements in the bearing surface.

Mineral wool and asbestos fibers are comparable if not equivalent in properties to those of glass and may be employed in this invention with quite fair results.

Also, fibrous glass may be combined with higher melting bearing metals and alloys although the contribution of this addition is here of less consequence as such materials are not as subject as babbitts to failure at high temperatures and are of sufiicient ruggedness to stand ordinary journal stresses. The melting points of such metals must, of course, be well below that of the fibrous glass in order not to melt or severely soften the glass.

In View of the performance of fibrous glass in creating rigid lands in the bearing surface, it may be presumed that minute glass beads or even flakes wouldalso serve well in this capacity. They, however, would pose more of a problem in dispersement through the molten metal as they would be inclined to float land would not have the self distributing character of the long fibers nor the loosely integrated mass of the latter. Also, the bead and flake particles would likely have no greater bonding effect than that of the crystals in conventional Babbitt alloys. While,

therefore,'not as suitable as the fibrous glass, beads and i fiakes incorporate the concept of this invention of utilizing glass particles in a metal bearing composition.

The surprising magnitude of the reinforcing effect of the glass addition in small proportions suggests that there may be a chemical action involved. It has been found that fractional percents of sodium and calcium act as hardening agents in lead and there is a possibility that under the high heat of contact between the fibrous glass and the molten metal that minute amounts of these elements are released from the glass composition or shared in a chemical compound. This theorical action could develop at least a hardened sheath or section around the fibers.

While certain specifications, temperatures and measurements have been recited herein they should not be considered as restrictive as others outside of the prescribed ranges may be utilized although likely with results not fully as satisfactory.

For instance, heaviei fibers than those recommended would have many attributes of the smaller sizes but would not have as much flexibility nor the endurance under pressure.

Other modifications in the disclosed embodiments may be envisioned without departing from the essence of the invention nor the scope of the appended claims.

I claim:

l. A plain journal bearing having a soft metal as a main component and elements of glass as a minor component, said elements being positioned generally in spaced relation within the soft metal, said minor component of glass elements being between three and six percent by volume of the main component of soft metal.

2. A plain journal bearing of the babbitt type, having a soft metal matrix and, as a minor constituent, hard particles dispersed therethrough, in which at least a portion of the hard particles are fibrous in form and of glass composition, said portion of the 4hard particles of glass composition not exceeding six percent by volume of the soft metal matrix. f

3. A plain journal bearing of predominantly lead composition having a minor component of fibrous glass embedded therein, said minor component of fibrous glass being between three and six percent by volume of the lead composition.

4. A plain journal bearing of predominantly tin composition having a minor component of fibrous glass embedded therein, said minor component of fibrous glass being between three and six percent by volume of the tin composition.

f 5. A plain journal bearing of soft metal having, as a minor constituent, a reinforcement of fibers, of a harder substance than the metal, embedded therein, said minor constituent of fibers being between three and six percent by volume ofthe soft metal.

6. A plain journal bearing having a metal with a melting point below that of glass as a main component and fibrous glass as a minor component, said component of fibrous glass being between three and six percent in volume of the metal component.

References Cited in the file of this patent UNITED STATES PATENTS 2,322,771 Palm I une 29, 1943 2,357,106 Grenet Aug. 29, 1944 2,559,572 Stalego July 3, 1951 OTHER REFERENCES Metallurgy `of Lead (first edition) (third impression), published by McGraw-Hill Book Co., Inc. (1918), see pp. 30-33.

Bearing Metals and Bearings, published by the Chemical Catalog Co., Inc. (1930), pages 365 thru 374 relied upon. 

1. A PLAIN JOURNAL BEARING HAVING A SOFT METAL AS A MAIN COMPONENT AND ELEMENTS OF GLASS AS A MINOR COMPONENT, SAID ELEMENTS BEING POSITIONED GENERALLY IN SPACED RELATION WITHIN THE SOFT METAL, SAID MINOR COMPONENT OF GLASS ELEMENTS BEING BETWEEN THREE AND SIX PERCENT BY VOLUME OF THE MAIN COMPONENT OF SOFT METAL. 